On 25 September 2009 Western leaders accused Iran of building a new and secret uranium enrichment facility, now known as the Fordow Fuel Enrichment Plant, in a mountain near the holy city of Qom. Iran had announced the facility to the International Atomic Energy Agency (IAEA) just days before and, Tehran claimed, well in advance of what it sees as its legal obligations. Western governments contended that the characteristics of the Fordow plant were inconsistent with a commercial facility and, therefore, inconsistent with a peaceful nuclear programme.

Estimates of Fordow’s capacity indicate that the situation is more complex than was first portrayed. According to design information recently submitted to the IAEA, Fordow will contain 3000 IR-1 centrifuges, the kind that are currently operating at the commercial Fuel Enrichment Plant at Natanz. Based on IR-1 performance so far, it is true that Fordow, as planned, does not make sense as a commercial uranium enrichment facility. But the plant by itself is too small for even a nuclear weapons programme.

Other strategic functions suggested by Iran, that Fordow will serve as a contingency plant to maintain enrichment in case Natanz were bombed or, according to a quasi-government website, that it may devalue and deter an attack altogether, are also undermined by the plant’s low capacity.

Fordow makes sense only within a context of increased separative capacity, coming either from higher per machine performance or from more machines. Iran seems to have acknowledged this problem with plans for new facilities and intentions to install better quality centrifuge models, which it has been testing since 2008. Iran’s declaration of plans to build ten new enrichment facilities has been widely prematurely dismissed in the West as little more than bravado, but it should be taken seriously. Fordow makes most sense as part of a network of similar facilities and has no logical justification with current design. Even this new announcement does not make Iranian intentions absolutely clear-cut: With increased capacity, the commercial, military and contingency justifications all become more plausible.

What is the IR-1?

Assessments of Fordow’s civilian or military capacity hinge on the performance of the IR-1, the only commercially operating centrifuge in Iran. These estimates have varied greatly, but IAEA reports now provide enough information to calculate the capacity of the IR-1 in actual use.

The IAEA accepts separative capacity as competition-sensitive, proprietary information that is legitimately protected, so it is not directly collected by IAEA inspectors. Iran has never published quantitative technical details of its centrifuges, except for a couple of statements by officials.

Past estimates of IR-1 separative capacity have ranged from 1.4 to 3 kg-SWU/year, which has proven to be 3-7 times higher than actually achieved performance. Given the lack of hard quantitative data, most Iran-watchers have been forced to make guesses based on analogues with the Pakistani P-1 model and its assumed early European prototypes. There is little consensus on what those European analogues are (whether the G-1, M4, CNOR or SNOR) and their performance is imperfectly known as well. Most information we do have on these machines comes from anonymous sources, such as unnamed Urenco, IAEA, intelligence or government officials, with presumed access to classified or confidential industry data but with unascertainable credibility. There have been some calculations based on physical characteristics of the machine (obtained through analogy or from the author’s estimates). Statements and interviews in the Iranian media on machine performance have dropped estimates to about 1.4 kg SWU/year. However, these lower estimates from Iranian officials need to be closely scrutinized because Iran views its nuclear programme as a symbol of national pride and has been known to embellish its nuclear achievements.

IR-1 performance

Centrifuges have been spinning at Natanz since 2003 and the agency publishes reports on their operation several times a year. However, the utility of hard data on actual IR-1 performance from IAEA onsite inspections has been overlooked. Current IR-1 performance at Natanz is the best estimate for near-term capacity at Fordow.

For material accountancy purposes, the IAEA records the degree of enrichment and amount of uranium hexafluoride that enters and leaves the cascades, as well as the number of operational centrifuges. Based on this information, we estimated the effective separative capacity of the IR-1 to be 0.44 kg-SWU per machine per year or 4 to 5 times less than the most widely-referenced values in the literature.

It has been no secret that Iran’s centrifuges have been and are not operating up to par. In 2008, an IAEA report stated that the “throughput of the facility has been well below its declared design capacity.” Individual IR-1s are still being tested at the pilot enrichment facility at Natanz, which indicates that Iran is still hoping to improve performance. Moreover, Iranian officials themselves have stated that they are not happy with IR-1 performance and hope to install new models at Fordow. The very high tails assay that Iran produces at Natanz is further tacit acknowledgement that their enrichment is inefficient and expensive.

The IAEA data applies only to the entire production of Natanz, not individual centrifuges. The facility production might be low because individual machines are performing poorly or they may be inefficiently linked into cascades or, most likely, both. Iran has said that A.Q. Khan’s clandestine procurement network offered the drawings of a second centrifuge model (the basis of three new models Iran has been testing) as a compensation for supplying defective IR-1 parts; poor components may be another reason that Iran is having difficulties getting the machines up to speed. In addition, inter-stage mixing and hold up during cascade operation contribute to separative work losses. So the performance of 164 connected machines is less than 164 times the performance of an individual machine.

We have to keep in mind that the IAEA data do not give us any information on why the performance is low, simply that it is. Whatever the reason for the performance shortfall, Iran has been operating the IR-1 for 7 years now, so we do not believe these are technical problems that are likely to be fixed overnight, hence our assumption that Natanz performance will be a good short-term predictor of Fordow performance.

Fordow’s potential

If estimates of Iranian enrichment capacity as a whole have been overstated, then estimates of how long Iran might take to enrich enough uranium for a nuclear weapon have been overstated as well. Based on current centrifuge performance at Natanz, it would take Fordow’s 3000 IR-1s close to a century to enrich a year’s fuel load for an average 1000MWe reactor starting with natural uranium and using typical global industrial tails assay. Therefore, by itself, Fordow does not make sense for a commercial enrichment programme. This fact, along with Fordow’s unusual location inside a tunnel in a mountain close to a Revolutionary Guard base equipped with air-defence systems, has been widely interpreted as sign of a military programme.

But Fordow’s capacity is also too small to be well-suited for a military programme. It would take over 3.4 years to enrich an IAEA ‘significant quantity,’ that is, enough for the simplest atomic bomb, of highly-enriched uranium from natural uranium, which we consider far too long to be a viable break out option, even if Fordow had been intended to remain a clandestine facility. In a year, the facility could produce a ‘significant quantity’ of bomb-grade material from already enriched reactor-grade uranium.

In either case, Iran would have to overcome safeguards hurdles. The first option would require diverting uranium hexafluoride from the conversion plant at Esfahan or constructing a clandestine conversion facility. Considering Iran’s poor track record of keeping nuclear activities secret, we believe the government is unlikely to pursue that option. In the second case, Iran would have to divert low-enriched uranium from Natanz. Given the long enrichment times needed at Fordow, the IAEA is highly certain to detect a diversion before Iran could enrich enough material for a even a single bomb.

One of several sites?

Fordow can make sense only if capacity is increased or it is one of similar sites. The facility’s current capacity is too small to make sense for either civil or military activity, therefore separative capacity needs to be increased. This can be achieved either by increasing per-machine performance or adding more machines.

Adding more machines at Fordow may be problematic if space is scarce, which might be expected in an underground tunnel. Centrifuge numbers could, however, be increased by constructing similar enrichment facilities at additional locations. In an article published in the Bulletin of the Atomic Scientists in November 2009, we speculated that Fordow is most likely one part of a network of similar facilities, which Iran could legally decide to construct in the near future.

Iran has indicated that it may pursue both options outlined above. It has reserved the right to install newer and better-performing centrifuge models as they become available. Tehran also declared that it will be constructing 10 additional enrichment plants – a plan that has been belittled by the West as unrealistic and simply an act of defiance. But it is a mistake to dismiss the claim, because with current capacity Fordow simply doesn’t make much sense. Although Iran has refused to disclose details on the planned facilities, we believe that the plants will be similar to Fordow – small and buried to protect against attack, because otherwise it would be more efficient to simply increase capacity at Natanz.

Increased separative capacity increases the plausibility of civil, military, and strategic justifications for Fordow, but not by the same degree. Dispersing the new facilities, keeping them small and forgoing economies of scale, and hardening against air attack, will increase costs and at first glance seems to prove that the facilities have a military, not civil, mission. But perhaps not.

We must keep in mind that even if the Iranian programme were purely civil, it is definitely not commercial. Decisions are not being made by a company but by a government bureaucracy, which is less concerned with simple cost and profit calculations. Natanz’s performance is disappointing to Iran. From a purely economic point of view, there is little doubt that it would be better to buy enrichment services on the international market. Tehran has decided that option is not reliable and has gone for independence. They must know this approach would be more expensive but were willing to pay the cost premium for strategic energy security reasons. In addition, Iran has staked enormous political prestige, both domestic and international, on their enrichment programme. So all economic arguments about the programme are suspect. In particular, just because something does not make commercial or economic sense does not mean that it must be, by default, a military programme.

Moreover, credible threats of military attack against Iran’s enrichment programme have been made or hinted at. Tehran may calculate that, while expensive, having a substantial slice of its capacity immune to attack is like paying for insurance – a cost incurred to reduce risk. Some Iranian sources have said that the purpose of the Fordow-like sites is to provide an invulnerable backup to Natanz, which would make an attack on Natanz less strategically useful since weapons-grade enrichment could take place elsewhere. This makes bombing the large safeguarded civil enrichment plant less attractive, and therefore less likely. That is, the existence of the Fordow sites deters attack on Natanz.

No outside power is threatening to attack Natanz because of its civil applications but because of its bomb-making potential. To deter attack, the Fordow sites must be able to duplicate the capabilities that would be targeted in Natanz. In other words, even if purely civil in mission, the Fordow sites would be sized around a nuclear weapon capability. Current centrifuges are so inefficient that even ten Fordows will have a problem supplying enough fuel-grade uranium for a civilian nuclear reactor, but would be a perfect size for a modest nuclear weapon production.

Iran has already announced intentions to build the new enrichment sites, so they will eventually fall under IAEA safeguards, making the illicit diversion of nuclear material difficult. Nevertheless, the facilities present a dangerous breakout potential. We believe that recent developments still leave some ambiguity about Iran’s intentions about building a nuclear weapon, but it is clear that it wants to maintain the potential. A greater enrichment capacity creates a greater danger that, if Iran makes the decision, it can expel IAEA inspectors and start weapons-grade enrichment in hardened underground facilities.

The circumstances surrounding Fordow are worrying. While not a smoking gun, the entire situation has increased suspicions about Iran’s intentions. Whether the new sites are intended primarily for civil or military ends, they serve a larger strategic purpose of increasing Iran’s future breakout potential in the event it wants to make a run for a nuclear arsenal. If Iran is worried about protecting it enrichment facilities, making political concessions with the IAEA for increased transparency would be more effective in reducing the chances of being bombed than equivocal hardening and dispersal.

Author Info:

Both authors are with the Federation of American Scientists. Ivanka Barzashka is a researcher for the federation’s Strategic Security Program, specialising in Iran’s nuclear capability and potential, and Ivan Oelrich is vice president of the same programme. Federation of American Scientists, 1725 DeSales Street, NW, 6th Floor, Washington, DC 20036, USA

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